Abstract: A spinal implant assembly is provided which has a stabilizer rod clamped into position within an anchor by means of a sliding closure member including a mating set screw or hook. The exterior faces of the anchor are contoured to optimize interface in the surgical setting. The anchor includes a U-shaped channel having multiple undercut surfaces such as grooves, which mate with flange like projections or “dovetails” of a closure member which is slid in a direction corresponding to the longitudinal axis of the rod. The closure member has on either side a flange mating with opposing recesses formed at the top of the U-shaped channel so as to lock the closure member in place. The set screw has an external hex head for tightening, and a plurality of radically extending prongs which are undercut and which mate with the recesses in the top of the U-shaped channel of the anchor. The hex head sheers at a necked area above the radial collar to provide for a flush surface relative to the closure member.